The interactions and mechanism by which estrogen induces type IV hyperlipidemia will be investigated in the chick liver model. The role of the nuclear estrogen receptor in modifying transcriptional events will be determined using both purified nuclei and chromatin. The differences in the molecular basis of induction of synthesis of two specific classes of lipoproteins, VLDL, will be studies using specific cDNA probes. One of the major lines of investigation will be purification of the nuclear form of the estrogen receptor. This molecule will then be used to study binding specificity of receptor to subcellular constituents and modification of in vitro transcriptional events. Such studies should allow the elucidation of the subcellular specificity of estrogen in inducing hyperlipoproteinmia.